1. Field of the Invention
The present invention relates to a navigation apparatus for setting and displaying a route leading from a current point (a specific point or a predetermined point etc.) to a destination point so as to assist driving of a mobile unit such as vehicle.
2. Description of the Related Art
Conventionally, it is required for a navigation apparatus that is mounted on a mobile unit such as car or ship, or is carried by a pedestrian, to accurately determine a current location and traveling direction. Also, it is required to display a map data corresponding to the current location, a location mark, a mark indicating the traveling direction leading to a destination point and other information requested by a user on a device such as display device, appropriately and rapidly.
A conventional navigation apparatus to be mounted on a car sets a route based on various input data such as starting and destination point and relevant map data, and calculates directions and distances, relative to the current location of the car, to provide guidance for the route in the forward direction.
Another conventional navigation apparatus includes a rerouting function for automatically performing a search for a new route from a current location to a predetermined destination point, when the location of a user vehicle traveling a designated route deviates from that route, or when data is obtained indicating that traffic along the route ahead is congested.
A general navigation apparatus searches a route depending upon not only a starting point (when a specific point is not designated, the position of the user vehicle is automatically set as the starting point) and a destination point (some points to be passed may be set between the starting point and the destination point), but also search conditions such as road data including distances, road widths, straight stretches and tolls, and traffic data including traffic congestion and road construction. The navigation apparatus designates a route that appears to be the optimal one, automatically or by user's selection.
However, there is a case where a better route exists depending upon time of day, the day of the week, the weather, or user's experience. In such a case, it may be possible to shorten the driving time or to ease the driving by selecting the better route even though the driving distance become longer than that of the route designated by the navigation apparatus. Since the conventional navigation apparatus does not take into account such user's experience and knowledge during the route setting process, an optimal route that is consonant with the user's intent can not be designated.
In case where the better route exists, the rerouting function is not activated in the conventional navigation apparatus until a user intentionally deviates from the designated route. Thus, during the period beginning with the deviation from the preset route and continuing until the search results are displayed, the user must drive without the route guidance. To avoid this phenomenon, the user must intentionally and manually activate the rerouting function before the user vehicle diverges from the designated route. Also, it is required for the user to designate points to be passed, turning direction and roads to be passed.